Referring to FIG. 1, an example vehicle 1 may include a lamp unit 100 for stably providing a driver with visibility or for informing other vehicles of the driving state of the vehicle 1, for example, when the outside is low.
A vehicular lamp unit may include a head lamp installed at the front of the vehicle and a rear lamp installed at the rear of the vehicle. The head lamp is a lamp that may illuminate the front of the vehicle to lighten the front during a night operation. The rear lamp may include a brake light that may be turned on when the driver operates a brake and a turn signal light that indicates a traveling direction of the vehicle.
Referring to FIG. 2, there is a growing interest in the vehicular lamp unit 100 that uses an energy-efficient laser light source 10. For example, light emitted from a laser diode is straight, an irradiation distance thereof is long, and may not interfere with a field of view of an oncoming vehicle.
A white lamp may be implemented using the laser diode(s).
For example, light emitted from three types of laser diodes may be mixed to implement white light. In this case, each of the three laser diodes may emit light of three primary colors.
As an another example, light emitted from a blue laser diode may be converted into yellow light, and then mixed with light emitted from the blue laser diode to implement white light. In this example, white light may be implemented using one type of laser.
In some examples, a phosphor may optically convert blue light emitted from the laser diode. In this case, the laser diode emits light with very high output power, and when light emitted from the laser diode is optically converted, a temperature of the phosphor may rise to 150° C. or more.
In the case of a resin phosphor and a phosphor-in-glass (PIG, hereinafter referred to as “glass phosphor”) which have been conventionally used for an LED light source, thermal quenching may occur during an optical conversion process of laser light.
In some examples, yellow light optically converted from the phosphor may be scattered and widely spread, and accordingly, part of the yellow light, which is optically converted in the phosphor, may be emitted to the outside without being mixed with the blue light. In this case, yellow ring may be generated, in which yellow light is emitted to the periphery of a light emitting region of the laser light source.